RAMALLAH, West Bank – At the top of the list of Palestinian prisoners likely to be freed in a possible swap for an Israeli soldier is a firebrand politician many Palestinians believe is a likely future president who can pull them out of their current political deadlock. But if released — not a sure thing — Marwan Barghouti would face a rancorous Palestinian political split, an Israeli government resistant to concessions and possible challenges from within his own party. Barghouti, 50, took a hard-line stance toward Israel in a letter from his prison cell read to supporters on Tuesday. He called for a diplomatic boycott, said negotiations have reached a dead end and claimed Israel's government is not a partner for peace. Gaza's militant Islamic Hamas rulers seek to win freedom hundreds of Palestinian prisoners, including Barghouti, in exchange for the Israeli solider, Sgt. Gilad Schalit, captured by Gaza militants in a cross-border raid in 2006. Despite reports that talks in Cairo to finalize the deal appeared to be making progress, Israeli Prime Minister Benjamin Netanyahu on Tuesday tried to lower expectations. "There is no deal yet and there might not be one," he said. Hamas official Mohammed Nazzal in Damascus said Israel still had reservations over releasing some prisoners sought by Hamas who have "long prison terms." "If Israel reacts with flexibility it will end soon, or it will be postponed indefinitely. During the next few days the picture will become clear," he said. Israel has been eager to win the release of Schalit, but throughout negotiations has been reluctant to release Palestinians who were involved in killings of Israelis. Sealing a deal would also be a public boost for Hamas. It could tout the prisoners' release as proof the militant movement can win concessions from Israel at a time when its rival Palestinian President Mahmoud Abbas is looking ineffective to Palestinians at the negotiating table, despite support from the United States. It may also lead to some easing of Israel's punishing blockade of the Hamas-ruled Gaza Strip, though it is unlikely Israel would significantly open the territory. The talks come at a time of crisis for the Palestinians. They are torn between rival governments — Hamas in Gaza, Abbas's Fatah in the West Bank. Abbas has said he wants to quit his job out of frustration over stalemated peace efforts with Israel; with no obvious successor, his leaving could spark a leadership struggle among the Palestinians and throw already declining peace efforts deeper into turmoil. In this context, Barghouti's supporters often bill him as a figure who can lead the Palestinians out of their impasse. "He'll be a way out for the Palestinian people, for Fatah, for Hamas, for the Palestinian factions, and even for the international community," said Khader Shkirat, Barghouti's lawyer. Shkirat, the lawyer, said Barghouti supports "the principle of negotiations" with Israel but that they should be coupled with "actions on the ground that fight the occupation," including demonstrations, sit-ins and "all types of peaceful, popular resistance." Polls show the diminutive, chubby Barghouti is the most popular Palestinian leader since the late Yasser Arafat. The former leader of Arafat's venerable Fatah movement in the West Bank, he has avoided the reputation for corruption that has tarnished many Fatah members and undermined the movement's popularity. He also enjoys a man-of-the-people reputation that transcends many of the rifts in Palestinian society. He is secular but works with Islamists. He supports negotiations with Israel, speaks fluent Hebrew and has Israeli friends. He turned more militant during a Palestinian uprising that began in 2000, launching anti-Israel diatribes. Israel locked him up seven years ago after convicting him of involvement in attacks that killed four Israelis and a Greek monk. He is serving five consecutive life terms. "There is no partner for peace in Israel," he wrote, "only a radical right-wing government that hangs onto settlements and occupation."